Patent GB-646359-A (GB)
Title: Improvements in or relating to a device for transmitting compressional vibrations along a continuous metal conductor
IPC: H04B11/00
Filed: 1945-07-21
Abstract: 646,359. Signalling by compressional waves in solids. STEVENS, A. H. (Submarine Signal Co.). July 21, 1945, No. 18762. [A Specification was laid open to inspection under Sect. 91 of the Acts, April 5, 1946.] [Class 118 (ii)] [Also in Group XXXIX] A device for transmitting compressional vibrations along a continuous metallic conductor comprises means externally projecting laterally in all directions from the conductor on which are mounted a plurality of circumferentially disposed electro-mechanical transducers. The device is particularly suitable for signalling along oil pipe-lines. In the embodiment of Fig. 1, a heavy collar 2 is clamped around the pipe 1 and has embedded in one face magneto-strictive elements 11 arranged in concentric rings and each surrounded by an energizing coil 12. A protective cover-plate 15 is fitted. Electric oscillations may be applied to the coils 12 by a signalling key, the resulting vibration of the magneto-strictive elements 11 causing longitudinal vibrations in the pipe 1 which are received at a similar distant device and reconverted into electrical energy and then into sound. Valves in the pipe system are byepassed by a welded metallic connection. The collar 2 may be formed integrally with the pipe itself and may taper to the diameter of the pipe 1 in an exponential or other curve as in Fig. 4 to provide uni-directional transmission. In addition a section 40 of the pipe may be made of a material such as lead which reflects most of the vibrations reaching it. A tapered collar 54, Fig. 5a, may be fitted at the end of a pipe 52, the fluid to be transported entering from a perpendicular branch pipe 50<SP>1</SP>. The branch 50<SP>1</SP> is of elongated or elliptical cross-section where it joins the main pipe 52 in order to maintain substantially constant the cross-sectional area of the metal of the main pipe 52 and allow unimpeded transmission of the sonic vibrations along the main pipe 52. In a further modification (Fig. 7, not shown), magneto-strictive elements are mounted between two spaced flanges on the pipe, or between a heavy collar and a flange (Fig. 8, not shown). In a further modification (Figs. 9, 10) two halves of a heavy collar 100 are clamped around the pipe 99, one face being perpendicular to the axis of the pipe and one face tapering to the size of the pipe. On the perpendicular face piezo-electric crystals 102 (preferably of Rochelle salt) are arranged in concentric rings in an annular depression 101. The crystals are electrically excited via electrodes 103 on either side of each crystal by a speech-modulated carrier frequency. Specification 276,374, [Class 118 (ii)], is referred to. The Specification as open to inspection under Sect. 91 comprises also a magneto-strictive rod mounted between two semi-conical caps, one rod being mounted on each side of a running rail on a railway. The Specification also comprises a diaphragm device for transmitting compressional waves through the fluid in the pipe. This subject-matter does not appear in the Specification as accepted.